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J Knopp

Publications and source records attributed to J Knopp.

At least 55 records · Page 3Linked to original sources
PubMed1984

Effect of hypothalamic extracts of rats of various age on pituitary adenylate cyclase in vitro.

Adenylate cyclase activity in rat pituitary gland in vitro after the addition of hypothalamic extracts from rats of different age was investigated. Hypothalamic extracts from fetuses, 20 day-old and adult rats significantly increased the adenylate cyclase activity in pituitary of the adult rat incubated in vitro. However, any similar stimulatory effect was not found after the addition of extracts from 1 or 5 day-old rats. These results show possibly age dependent differences in the content of substances which stimulate the adenylate cyclase activity in the hypothalamus.

Adenylyl Cyclases↗
PubMed1984

Specific phosphorylation of nuclear non-histone proteins of rat liver after thyreoidectomy and T4 treatment.

The effect of thyroxine (T4) on phosphorylation of non-histone proteins in rat liver nuclei was studied. Non-histone proteins obtained by extracting liver nuclei with 0.4 mol X l-1 KCl from normal (N), hypothyroid (Tx) and Tx rats treated with T4 (100 micrograms kg-1 B.W.), respectively, were incubated with 32P-ATP at 30 degrees C for 5 min followed by sodium dodecyl sulfate-gradient polyacrylamide gel electrophoresis and autoradiographic analysis. Endogenous phosphorylation in Tx rats was decreased. In T4 treated Tx rats phosphorylation of some proteins was recovered, however the 84 X 10(3) mol wt protein was not completely recovered. Phosphorylation of nuclear nonhistone proteins was not altered by the addition cAMP into the incubation. These findings show that in vitro phosphorylation of non-histone proteins of the rat liver nuclei occurs in some specific fractions which may be thyroid hormone dependent.

Animals↗
PubMed1983

Effect of hypophysectomy and administration of TSH on the activity of monoamine oxidase in the thyroid gland of rats.

The thyroid monoamine oxidase (MAO) activity was measured in rats after hypophysectomy and TSH treatment to find out whether the thyroid MAO activity can be modified with TSH. Hypophysectomy decreased MAO activity in the thyroid gland of rats. The administration of TSH (2.5 U kg-1 daily for 5 days) to hypophysectomized rats increased MAO activity and fully compensated the absence of the pituitary. These data suggest that the thyroid gland MAO activity is under the regulatory influence of TSH.

Animals↗
PubMed1983

Nuclear receptors for thyroxine in rat liver during postnatal development in relation to DNA-dependent RNA polymerase activity.

Specific binding of 125I-thyroxine on liver nuclear extract of rat fetuses aged 15 and 18 days, of young rats aged 1, 2, 7, 12-14 and 18 days and of adult rats was quantified. The highest value representing the capacity of specific 125I-thyroxine binding was noted in rats aged 7 days. A marked diminution of specific 125I-thyroxine binding was demonstrated in rats aged 12-14 days. Practically the same values of Ka in liver nuclear extract were found in fetuses aged 18 days (Ka = 4.44 X 10(9) 1 mol-1) and in a group of young animals aged 7 days (Ka = 4.17 X 10(9) 1 mol-1). In nuclear extract of the animals aged 12-14 days and in adult rats diminished values (Ka = 2.72 X 10(9) 1 mol-1 and Ka = 1.18 X 10(9) 1 mol-1, respectively) were noted in comparison with the above-mentioned groups of rats. A positive correlation between the binding of 125I-thyroxine and Mn2+-activated DNA-dependent RNA polymerase activity in liver nuclei of rats aged 4 and 14 days and adult rats was found (r = 0.700). These results support the suggestion that thyroxine in the perinatal period of life plays an important role in the induction of mRNA.

Animals↗
PubMed1983

Rat thymus: demonstration of specific thyroxine receptors in nuclear extract.

Nuclear protein fraction from the nuclei of rat thymus was prepared by extraction in 0.4 mol l-1 NaCl and the presence of saturable thyroxine binding sites was demonstrated. Scatchard analysis revealed one class of high affinity binding sites with Ka = 4.15 X 10(9) 1 mol-1, the maximum binding capacity (expressed as number of ligand molecules per mg of protein) of 5.56 +/- 1.37 X 10(10), was found. Amino acid composition (expressed as mumol per mg of protein) of acid hydrolyzates of rat thymus and liver crude "receptors" for thyroid hormones is presented. The results show that the nuclear protein fraction of thymus, responsible for thyroid hormone binding shows some basic characteristics of non-histone proteins and differs in concentration of lysine, histidine, aspartic acid, proline, methionine and slightly in concentration of glycine, isoleucine and phenylalanine from that obtained from the liver. The data suggest that the rat thymus might be considered as a target tissue for thyroxine.

Amino Acids↗
PubMed1982

The nature of inhibition of thyroid monoamine oxidase by thyroxine in rat thyroid.

The effect of thyroxine on rat thyroid monoamine oxidase (MAO) activity in vivo and in vitro was studied in order to evaluate the nature of the inhibition of the enzyme. Monoamine oxidase activity was measured in rat thyroid homogenate. Thyroxine (200 micrograms kg-1) or triiodothyronine (40 micrograms kg-1) injected in vivo inhibited the activity of monoamine oxidase (MAO) significantly (P less than 0.05). Thyroxine (T4), 10 micrograms added to the incubation mixture during 20 min also inhibited MAO activity in thyroid homogenate. A Lineweaver-Burk plot of the data obtained shows that the inhibition is of the uncompetitive type.

Animals↗
PubMed1981

Effect of thiol blocking agents on the binding of T3 and T4 in rat liver nuclear extract.

Liver nuclei bind thyroid hormones (T3 and T4) with different binding affinities. In out studies it was estimated that the apparent association constant (Ka) in the liver nuclei for T3 was 8.8 X 10(10) l mol-1 and for T4 was 4.1 X 10(9) l mol-1. We have found that the binding sites for T4 are also saturated by an excess of unlabelled T4 and that saturation was dependent on the purification step of liver binding proteins. In liver nuclear extracts with 0.4 mol l-1 KCl the specific binding of T3 and T4 was blocked with a typical -SH blocking agent N-ethylmaleinimide (NEM) and by new types of -SH blocking agents such as p-bromphenylisothiocyanate (p-BPI) and 2,3 dicyano-1,4-dithio-9,10 antrachinone (Delan). NEM and p-BPI increased the non-specific binding of T4 and completely abolished specific binding. All these agents blocked the specific binding of T3. These results demonstrate that T3 and T4 binding sites in the liver nuclei may not be altogether identical and that the different effects of -SH blocking agents on the binding of T3 and T4 is probably associated with the structural configuration of these drugs.

Animals↗
PubMed1981

Specific thyroxine nuclear receptors: DEAE-sephadex chromatography of rat liver nuclear extract.

Specific binding of thyroxine to protein fraction obtained by DEAE-Sephadex chromatography of dialyzed (0.4 mol 1-1 KCl) nuclear extract of purified rat liver nuclei was studied. A procedure for several-fold purification of thyroxine nuclear receptor included isolation of purified rat liver nuclei (by centrifugation through 1.7 mol 1-1 sucrose), extraction, dialysis, Sephadex G-100 and DEAE-Sephadex A-50 chromatography. It was found that a protein peak eluting at 0.05 mol 1-1 NaCl does not show any fraction specifically binding thyroxine. However, specific binding of nuclear receptor for thyroxine was found in a peak eluting at 0.20 mol 1-1 NaCl, the capacity being about 600 fmol mg-1 protein. Moreover, total binding capacity of intact rat liver homogenate, nuclei, non-dialyzed and dialyzed (0.4 mol 1-1 KCl) nuclear extract, Sephadex G-100 and DEAE-Sephadex A-50 chromatography protein fractions for thyroxine was tested. A marked increase (about 20 fold) in the total thyroxine binding expressed in fmol mg-1 of protein in DEAE-Sephadex A-50 eluate was found as compared to whole nuclei, nuclear extract or Sephadex G-100 chromatography fractions. Partial fractionation of rat liver nuclear extract combined with thyroxine binding studies demonstrated that rat liver nuclei contain a non-histone protein fraction--a receptor that is responsible for a specific binding of thyroxine.

Animals↗
PubMed1981

[Antibodies against tumor associated antigens of human bronchogenic carcinoma: demonstration by anti-complement immunofluorescence (author's transl)].

A method of anti-complement immunofluorescence is described for semiquantitative measurement of antibodies in 281 sera samples obtained from patients with bronchogenic carcinoma. Tests were performed on frozen sections of 17 human bronchogenic carcinoma. - 168 sera obtained from healthy persons were used as control. Tumor and control sera were also tested on frozen sections of 10 normal lungs. - The intensity of fluorescence was measured by incident light with the aid of a Leitz microscope photometer. In comparison to control sera the mean values of fluorescence intensity of the tested 281 tumor sera were significantly higher when frozen sections of bronchogenic carcinoma were used. - In order to allow for the different content of antigens in the bronchogenic carcinoma we have calculated the rations of the tested tumor and control sera on tumor and normal sections. - The percentage of positive results showed strong dependence on the histological type of the bronchogenic carcinoma used as frozen section and differed between 16,3 and 69,1%. The highest percentage of positive reactions resulted when tumor sera were tested on frozen sections of undifferentiated bronchogenic carcinoma. Besides that sera from patients suffering from small cell bronchogenic carcinoma gave more positive results than sera from patients with other bronchogenic carcinoma. - In 78,3% of the carcinoma were tested on frozen sections of undifferentiated bronchogenic carcinoma.

Animals↗
PubMed1980

Changes in adenylate cyclase activity in rat pituitary after TRH and T3 injection in vivo.

Increased activity of adenylate cyclase in whole anterior pituitary was repeatedly found in groups of 3-6 adult male rats 5 min after iv injection of 10, 100 and 200 nmol of TRH kg-1. After the administration of 100 nmol TRH kg-1 the activity of adenylate cyclase was significantly increased at 2, 5, 10 and 30 min with a peak level at 5 min, while at 60 min the values did not differ from controls. The level of TSH in serum was significantly increased in all TRH injected groups with a peak value at 10 min, while no dose-response relationship was found at 5 min. Finally, the activity of adenylate cyclase was significantly decreased in animals injected with 20 nmol of L-triiodothyronine kg-1 180 min before sacrifice, the decrease being not overcome by 100 nmol TRH kg-1 injected 5 min before sacrifice.

Adenylyl Cyclases↗
PubMed1980

In vitro effect of TRH on adenylate cyclase and cAMP in rat anterior pituitary and on TSH and PRL release into incubation medium.

Rat anterior pituitaries were incubated for 20 min with 1, 5 or 20 nmol TRH ml-1 and cAMP was measured in the homogenate of pituitary tissue after incubation, while TSH and PRL release into the medium was estimated with the aid of specific radioimmunoassay. In a similar experiment the activity of adenylate cyclase in pituitary homogenates was measured after the incubation with 0.5, 1.0 or 5.0 nmol TRH ml-1. Significant increase of TSH and PRL in the medium was found after 5 and 20 nmol TRH ml-1, while cAMP was significantly increased after 20 nmol TRH ml-1 only. The activity of adenylate cyclase was significantly increased after all doses of TRH used. In general, these findings are consistent with current views on the effect of hypothalamic hormones via adenylate cyclase - cAMP system and show that the responsiveness and sensitivity of an in vitro system using whole pituitaries appears to be less that of in vivo system.

Adenylyl Cyclases↗
PubMed1980

Thyroid hormone binding sites in rat liver nuclear fraction.

The specific binding of 125I-thyroxine and 125I-triiodothyronine in rat liver nuclei and 0.4 mol 1(-1) KCl nuclear extract is presented. The Scatchard plot analysis for triiodothyronine calculated from the competition curve of isolated nuclei gives Ka = 1.3 x 10(9) mol-1 and from that of nuclear extract gives Ka in the range of 10(8)--10(10) 1 mol-1. Crude nuclear extract of rat liver nuclei (0.4 mol 1(-1) KCl, 5 mmol 1(-1) dithiothreitol) after removing of inorganic KCl on G-25 Sephadex was fractionated on G-100 Sephadex. Two different nuclear protein fractions were obtained and the distribution of 125I-thyroxine and 125I-triiodothyronine in these protein components was tested. 125I-thyroxine binds clearly on both protein fractions, whereas 125I-triiodothyronine binding was found only in the major protein component. The fractionation of nuclear extract incubated with labelled thyroid hormones with or without the excess of 0.04 nmol of thyroxine or triiodothyronine demonstrate a specific binding of both thyroid hormones to major protein component and nonspecific binding of thyroxine to a fraction representing the minor protein component.

Animals↗
PubMed1980

Differences in growth and thyroid activity persisting in adult rats reared in nests of different sizes during suckling period.

The undernutrition or overnutrition during a suckling period achieved by adjusting the number of infants per lactating rat to 4 (overfed-0), 8 (control-C) or 14 (underfed-U) resulted in long lasting differences in body weight. The consumption of the diet in 260-day old males and females was similar in all experimental groups if expressed per unit of body weight, thus suggesting the differences in energy utilization. An increase of thyroid hormone secretion rate was found in U rats aged 30, 120 and 300 days as compared to 0 ones. Serum TSH level was also higher in U rats at the age of 30 days and 1 year. However, serum thyroxine level in U groups was either higher or similar as in controls. Paper chromatography of thyroglobulin hydrolyzate 24 h after 125I injection to 300 days old males showed a decrease of radioactivity in iodide area in U animals and an increase in triiodothyronine area in 0 animals. The analysis of thyroglobulin from 200 days old females on linear sucrose gradient did not reveal any rough change in its iodination. The results indicate an increase of thyroid activity in adult, previously moderately underfed male and female rats. Some changes in feedback sensitivity of hypothalamo-pituitary-thyroid axis may presumably also occur in these animals.

Animals↗